Brainwashing

Evil forces do take control of our life, but it is within our power to free ourselves from falling under their subjection. There are, therefore, specific actions that Bahá’ís can take when confronted with [the] kind of situation of which you write, but the principal way in which they can overcome them is to deepen themselves in the Teachings of Bahá’u’lláh so that they will come to recognize the lack of any true reality to such negative forces.(Universal House of Justice, Lights of Guidance, p. 520).

The heart must needs therefore be cleansed from the idle sayings of men, and sanctified from every earthly affection, so that it may discover the hidden meaning of divine inspiration, and become the treasury of the mysteries of divine knowledge.(Bahá’u’lláh, Kitáb-i-Íqán, p. 70).

There is no power exercised over the people by those evil souls that have passed away. Good is stronger than evil and even when alive they had very little power. How much less have they after they are dead …(‘Abdu’l-Bahá, Lights of Guidance, p. 520.)

You should not be afraid anyone can affect your mind. Even when we want to catch the thoughts of those we love most we cannot do so, how much less other people succeed in penetrating our minds.(Shoghi Effendi, Lights of Guidance, p. 518)